Various attempts have been made in the art to address the need to provide motorists with advance information relating to hazardous road conditions in order to permit them to take defensive action and avoid accidents.
For example, U.S. Pat. No. 6,487,500 (Lemelson et al) issued Nov. 26, 2002 entitled “GPS vehicle collision avoidance warning and control system and method” discloses a GPS based location system that continuously determines a vehicle's tracking position on a pathway with centimeter accuracy. The GPS-based position is communicated with selected other status information to other vehicles in the vicinity, to a station and/or to one of a plurality of control centers, which relay to the vehicle each of the other vehicles' status information and kinematic tracking position. Objects are detected from all directions by various sensors and data are computer processed and analyzed in neural networks on-board the vehicle to identify, rank, and evaluate collision hazards/objects allowing automatic control of the vehicle.
U.S. Pat. No. 5,982,278 (Cuvelier) issued Nov. 9, 1999 and entitled “Road monitoring device” discloses a device for improving vehicle driving safety and comfort. Information relating to road markings encountered during a journey is transmitted to the vehicle, the position of the vehicle on the driving surface is continuously monitored, and the road surface is checked for the presence of foreign matter such as mud, snow, ice, etc. A set of transmitting-receiving sensors suitably arranged on the vehicle and facing the driving surface continuously observes changes in the reflective properties of the observed areas within the sensitivity range thereof. Sensors detect markings defiling lanes and shoulders lined with grassy, gravelly or sandy areas as soon as the vehicle approaches or drives over them. Signals from the sensors are processed by an electronic unit controlling an on-board signaling system linked to an alarm system for warning the driver of road hazards and possible unsafe driving, such as straying off-course, speeding, etc.
Information relating to upcoming traffic signs are conveyed to the motorist by means of suitable sensors, such as transmitters, which emit waves that are reflected off the road surface. An example is described with reference to FIG. 6 of U.S. Pat. No. 5,982,278 wherein a vehicle's speed is checked when approaching a hazardous bend. Spaced-apart sensors built into the road surface, at right angles to the road axis, detect the vehicle's presence and, based on the time difference between the vehicle passing over successive sensors, calculate the vehicle's speed. If the vehicle speed exceeds then maximum permitted speed for the location, an alarm is given prompting the motorist to take remedial action.
FIG. 7 of U.S. Pat. No. 5,982,278 shows an extension of this concept where sensors are disposed in the road surface prior to a junction so as to assess the approaching speed of the vehicle and to allow an on-board speed controller to reduce the speed commensurate with the need to stop at the junction.
Such sensors may be used to convey to the motorist information relating to traffic signs, such as STOP, but this requires that sensors be built into the road surface, requiring significant modification to the existing infrastructure.
It would therefore be desirable to provide a road safety warning system that responds to road signs for conveying warnings to a motorist whose approach speed is deemed dangerous, but without the need to modify the highway.